There's a good NBC Dateline episode on the murder and the trial.
Momeni was convicted of 2nd degree murder in December. The motive was murky. The prosecution claimed that Momeni stabbed Lee because he believed Lee's dealer had sexually assaulted his sister Khazar. Khazar testified that she had been assaulted. Momeni claimed he didn't believe his sister. In any case, Khazar and the drug dealer continued to hang out after the murder.
The purported motive is odd and seems incomplete. That's probably because Lee was reluctant to talk sh** about his friends, so no one knew what was up. As PPs said, Momeni and/or his sister may have wanted a come up from Lee.
The Dateline episode has interviews with Lee's ex-wife, Momeni'a mother and newly available footage of Lee right before the murder.
https://www.nbcnews.com/dateline/in-the-news/dateline-full-episode-under-the-bay-bridge-rcna191821. If you don't have Peacock or NBC, it's available as a podcast.